Device for transforming electrical variations into sound variations



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OR 1,81 yo801 DEVICE FOR TRANSFORMING ELECTRICAL VARIATIONS INTO SOUND VARIATIONS Filed April 1, 1930 Invent or:

Friedrich WHehLgmfls,

BHMWZZM' Patented July 14, 1931 UNITED STATES PATENT OFFICE FRIEDRICH W. HEHLGANS, OF BERLIN-HERMSDORF, GERMANY, ASSIGNOR TO GENERAL ELECTRIC COMPANY, A CORPORATION OF NEW YORK DEVICE FOR TRANSFORMING ELECTRICAL VARIATIONS INTO SOUND VARIATIONS Application filed April 1, 1930, Serial No. 440,855, and in Germany April 23, 1929.

My invention relates to devices for producing light variations in response to electrical variations, such devices depending for their operation on a rotational effect of the plane of polarization of the light when passed through certain liquids under electrical influcncc. ()no form of such devices is that commonly known as the Kerr cell inasmuch as it makes use of the Kerr effect. In this cell two electrodes are separated by the liquid through which the light is passed, the electrodes being adapted to be subjected to a variable potential difference. The liquid commonly employed in these cells is nitrobenzol and when the cells are used out-ofdoors during cold weather, as for example in making sound record films or picture-sound films. it has been found that the cells become inoperative at temperatures below 5 C. as this is approximately the freezing temperature of the nitrobenzol used therein.

It is one object of my invention to provide an improved transforming device of the character referred to above which can be used when subjected to lower temperatures than heretofore. and another object is the provision of an improved device of that character in the liquid of which less light absorption shall occur.

I have found that these objects may be attained by the use of toluidin as the liquid which separates the electrodes and through which the light is passed, since it freezes at 1 a much lower temperature than nitrobenzol. I mav use either orthoor metatoluidin but I prefer to use for this purpose orthotoluidin, for since it has a freezing point of approximately-20 C. it can be used at temperatures which are far below those at which nitrobenzol may be used. Moreover with orthotoluidin there is less light absorption than with nitrobenzol being in contradistinction thereto a colorless liquid.

Referring to the single figure of the drawing wherein is represented by a fragmentary cross sectional view an embodiment of my invention, the electrodes 1 and 2 of a Kerr cell are shown spaced by the liquid 3 which is orthotoluidin through which thelight is adapted to be passed'in the usual and well understood manner.

What I claim as new and desire to secure by Letters Patent of the United States, is:

0 1. A device for transforming electrical variations into variations of light including spaced electrodes and toluidin therebetwcen through which the light may be passed.

2. A Kerr cell having toluidin as the medium separating the electrodes thereof.

3; A Kerr cell having a pair of spaced electrodes and orthotoluidin in the space between said electrodes and through which the light is passed.

In witness whereof, I have hereunto set my hand this 14th day of March. 1930.

FRIEDRICH WV. HEHLGANS. 

